And Haku is magical, too. He is immortal, born when his river was first created, since he is the spirit of it. And the Kohaku River wasn't there (and filled in) for only 12 years. He, although doesn't look like it, is much older than Chihiro.
Haku sure is magical creature, as a dragon and a river spirit at that. As for his real age, we are not sure since the details have not been revealed. But definitely, if you want to compare between Haku and Chihiro, Haku sure is much older than she is.
So, is it totally creepy that him and Chihiro are a thing?
Who knows, maybe Haku went and reincarnate into human? That's another topic (new discussion if you wish) anyway. xD
Nowadays, with all the bad news out there, people killing other people, abuse, violence and such such...what makes a person human? Do human that we know now really a person to do all these horrible things to each other? If Haku and Chihiro finally gets together, at least we can be sure that Haku will threat her well even when he's not "human".
That's not about his true age and definitely shouldn't be on this topic, even though it was slightly changing to "if Haku made himself human". That "paragraph" shouldn't even be on a topic at all. Humans have always done that; and to "fight" your quote, even lovebirds get in arguments and have verbal abuse.
Chronologically, he's likely as old as the river he once resided in. Physically, he's likely two-four years older than Chihiro.